Face detection

Table of Contents

Haar-like features

A Haar-like feature considers adjacent rectangular regions at a
specific location in a detection window, sums up the pixel intensities
in each region and calculates the difference between these sums. This
difference is then used to categorize subsections of an image. For
example, let us say we have an image database with human faces. It is
a common observation that among all faces the region of the eyes is
darker than the region of the cheeks. Therefore a common haar feature
for face detection is a set of two adjacent rectangles that lie above
the eye and the cheek region. The position of these rectangles is
defined relative to a detection window that acts like a bounding box
to the target object (the face in this case).